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We have obtained ultrahigh room-temperature (RT) hole Hall and effective mobility in Si0.3Ge0.7/Ge/Si0.3Ge0.7 heterostructures with very small parallel conduction. Reducing parallel conduction was achieved by employing Sb doping in Si0.3Ge0.7 buffer layers, which drastically increased RT hole Hall mobility up to 2100 cm2/V s in the strained Ge channel modulation-doped structures and improved device characteristics of the p-type metal–oxide–semiconductor field-effect transistors with the strained Ge channel. The peak effective mobility reached to 2700 cm2/V s at RT, which was much higher than the bulk Ge drift mobility.

Electrical properties of Ge-rich SiGe-on-insulator (SGOI) and Ge-on-insulator (GOI) structures fabricated by Ge condensation process have been studied. The SGOI and GOI structures for Ge composition, xGe, larger than 0.4 exhibit p-type conduction. The hole density is found to rapidly increase from 1016 to 1018 cm-3 with an increase in xGe during the Ge condensation and to decrease down to low-1017 cm-3 when xGe reaches unity. Analyses of scanning spreading resistance microscopy have directly revealed that the SGOI and GOI structures are highly conductive along the crosshatched slip bands formed during the condensation, meaning that the holes are induced along the slip bands in SGOI and GOI films. As a result, it is concluded that the hole induced during the Ge condensation is strongly associated with the slip band formation.